The present invention relates generally to explosive projectiles, and particularly to explosive projectiles such as ammunition useful in military training and practice exercises.
In military operations, large explosives projectiles such as those fired from stationary gun emplacements and tanks are still in common use, and military personnel must receive training and maintain proficiency therewith by constant practice. This is particularly important in the instance of mobile armored troop units. Due to the limited sized training ranges encountered in the areas in which armored troop units are deployed, tank gunnery for practice or training has been severely hampered, as it is necessary to provide adequate safety measures to facilitate the involvement of troops, and to secure the safety of adjoining civilian populations. In the past, personnel safety was achieved by limiting the firing to fixed position-fixed target gunnery problems, where the super elevation of the tank gun could be observed and closely controlled.
Recently, increased emphasis has been placed on armored and combined arms operations, resulting in a change in the training doctrine for these types of units. Emphasis has shifted to the simulation of actual tank-to-tank firing. In such new training environment, close control of tank gun super-elevation becomes extremely difficult, and the possibility of a training round exceeding the safety limits of the range and thereby endangering adjacent individuals and property is increased.
Applicants are aware of certain mechanisms known in the prior art as resonance tubes which have displayed some utility in connection with explosive charges, and have accordingly been utilized as explosion initiators. Specifically, U.S. Pat. No. 3,985,058 to Corrado et al., and U.S. Pat. No. 3,994,232 to Rakowsky et al., both assigned to the assignee of the present invention, disclose explosive initiators or actuators utilizing the conversion of gas movement to thermal energy by means of a device known as a "resonance tube", which comprises a cavity having an open end axially aligned with a suitable high velocity gas flow field. In the instance where instabilities in the impinging flow field are in synchronization with the natural frequency of the gas disposed in the resonance tube, high frequency oscillations are developed which cause the gas in the tube to undergo repeated cycles of periodic compression and expansion. This compression and expansion within the resonance tube produces irreversible temperature increases and develops a significant thermal energy concentrated at the closed end of the tube. See Hartmann, J., "On The Production Of Acoustic Waves By Means Of An Air-Jet Of A Velocity Exceeding That Of Sound", Phil. Mag., No. 7, Vol. 11, 72 pp. 733-749, April, 1931.